poof_he_is_gone

There is also https://www.fidsafe.com/

There is a podcast on the origin of the octothorpe name http://99percentinvisible.org/episode/octothorpe/

The public may own the physical artwork, but may not own the licensing to reproductions of it. Searching Cloud Gate on shutterstock.com will quickly show you that all of the images are editorial use only for this reason.